<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8" />
  <meta name="viewport" content="width=device-width, initial-scale=1.0" />
  <title>Document</title>
  <style>
    .box {
      /* 容器 */
      display: flex;
      justify-content: space-between;
      width: 500px;
      height: 500px;
      border: 2px solid red;
      margin: 50px auto;
    }

    .child {
      width: 80px;
      height: 80px;
    }

    .child1 {
      background-color: pink;
    }

    .child2 {
      /* 子项目 */
      align-self: flex-end;
      background-color: skyblue;
    }
  </style>
</head>

<body>
  <div class="box">
    <div class="child child1"></div>
    <div class="child child1"></div>
    <div class="child child2"></div>
    <div class="child child1"></div>
  </div>
</body>

</html>